Zeolites having double 6-membered rings have been studied as catalysts or adsorbents to be used in high-temperature, high-humidity environments.
In recent years, LEV-type zeolites have attracted attention as adsorbents or catalysts such as SCR catalysts for exhaust gas purification geared toward automotive use.
For example, in Patent Document 1 is disclosed an LEV-type zeolite having a silica-alumina molar ratio of from approximately 10 to approximately 300 synthesized using a quinuclidinium ion as a structure directing agent (also called an “SDA” hereafter).
In addition, in Patent Document 2 is disclosed an LEV-type zeolite synthesized using 1-adamantanamine as an SDA. The production method of this LEV-type zeolite tends to produce zeolite byproducts with a DDR structure as impurities at a high silica-alumina molar ratio. In Patent Document 2, substances reported as having a silica-alumina molar ratio of 34 includes zeolites with a DDR structure in addition to zeolites with an LEV structure. That is, in Patent Document 2, it has not been possible to produce a zeolite with a pure LEV structure having a silica-alumina ratio exceeding 25.
In addition, in Patent Document 3 is disclosed an LEV-type zeolite having a silica-alumina molar ratio of from approximately 10 to approximately 80 synthesized using a diethyl dimethyl ammonium ion as an SDA.
Further, selective catalytic reduction (called “SCR” hereafter) has been put into practical application as technology for reducing and detoxifying nitrogen oxides. Zeolites containing transition metals have thus been studied as zeolites suitable as catalysts to be used in SCR (called “SCR” catalysts hereafter).
In recent years, LEV-type zeolites have attracted attention as SCR catalysts for exhaust gas purification geared toward automotive use.
For example, in Patent Document 4 is disclosed a method using an LEV-zeolite as a method for converting nitrogen oxides to nitrogen using transition elements and small-pore zeolite having a maximum ring size based on eight tetrahedral atoms.
In addition, in Patent Document 5 is disclosed a Levyne molecular sieve containing copper and having a silica-alumina molar ratio of less than 30 and a copper-aluminum atomic ratio of less than 0.45.